1. Field of the Invention
The present invention relates to a method for dry-etching. More particularly, the present invention relates to a novel method for dry-etching a solid surface such as a silicon surface or a gallium arsenide surface, which is useful as a basic technology for the manufacture of semiconductor devices.
2. Description of Related Art
In the conventional manufacturing process of semiconductor devices, the etching method of a semiconductor crystal surface is popularly adopted as a basic technology for removing unnecessary portions of an insulating film or a metal thin film along a resist pattern at a high accuracy. As the degree of integration of semiconductor device has increased, however, the pattern width has become smaller. With chemical etching (wet etching) using a solution, which has been used as one etching method, it has now become difficult to cope with need of forming such a high-density pattern. Under these circumstances, attention has focused on a method known as dry-etching. The dry-etching method conducts etching in a relatively clean atmosphere under vacuum, and is therefore expected to enable processing of fine patterned devices.
For silicon (Si), a representative device material, for example, a dry-etching technique using fluorine and chlorine based halogen gases is known. This dry-etching technology makes it possible, in the case of silicon, to remove unnecessary portions of a fine pattern while keeping controllability on a necessary level, and is now considered as a major technique in practice.
In spite of the remarkable progress made in the dry-etching technique, in the case of silicon, it is the common practice to remove an oxide film On a silicon surface by the application of wet etching using an etching liquid such as hydrofluoric acid. The reason is that the oxide film on a silicon surface cannot effectively be removed by conventional dry-etching techniques. Application of wet etching may thus be inevitable.
In the case of this wet etching, however, a problem is that the surface undergoes a change in the course of passing silicon through vacuum after etching. Various measures are of course studied to maintain stability of the surface after removal of the oxide film. Along with the progress toward finer and higher-integration devices, no effective means has yet been found to stabilize the silicon surface after etching, but various problems have become more apparent.
And these problems have also become the same for the other various solid surfaces useful for fine semiconductor devices.
For the purpose of developing a dry-etching technique to form a fine pattern on semiconductor devices, there is naturally a demand for achieving a perfect dry-etching process in which removal of an oxide film on a solid surface such as silicon, GaAs and so on is accomplished by a dry-process. The present circumstances as described above however impose serious restrictions on achievement of a perfect dry-process. This is exerting an important influence also on practical development of the dry-etching technique itself for the formation of a pattern on the device material surface, and hinders efficient improvement permitting high-accuracy patterning.
The present invention was developed in view of the circumstances as described above, and has an object to provide a novel method for etching, which overcomes the restrictions in the conventional etching technique of solid surface, permits dry-etching at a high reproducibility by simple means also for an oxide film on a crystal surface, and allows achievement of a perfect dry-process.